The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Mobile telecommunication systems, such as those based on the 3GPP defined UMTS and Long Term Evolution (LTE) and Long Term Evolution Advanced (LTE-A) architecture, are able to support more sophisticated services than simple voice and messaging services offered by previous generations of mobile telecommunication systems. For example, with the improved radio interface and enhanced data rates provided by LTE systems, a user is able to enjoy high data rate applications such as video streaming and video conferencing on mobile communications devices that would previously only have been available via a fixed line data connection.
The demand to deploy fourth generation networks is therefore strong and the coverage area of these networks, i.e. geographic locations where access to the networks is possible, is expected to increase rapidly. However, although the coverage and capacity of fourth generation networks is expected to significantly exceed those of previous generations of communications networks, there are still limitations on network capacity and the geographical areas that can be served by such networks. These limitations may, for example, be particularly relevant in situations in which there is a desire for a group of terminal devices (communications devices) to exchange information with each other in a fast and reliable manner. In order to help address these limitations there have been proposed approaches in which terminal devices within a wireless telecommunications system may be configured to communicate data directly with one another without some or all their communications passing through an infrastructure equipment element, such as a base station. Such communications are commonly referred to generally as a device-to-device (D2D) communications. Many device-to-device communications may be transmitted by one device to a plurality of other devices in a broadcast like manner and so in that sense the phrase “device-to-device communications” also covers “device-to-devices communications”.
Thus, D2D communications allow communications devices that are in sufficiently close proximity to directly communicate with each other, both when within the coverage area of a network and when outside a network's coverage area (e.g. due to geographic restrictions on a network's extent or because the network has failed or is in effect unavailable to a terminal device because the network is overloaded). D2D communications can allow user data to be more efficiently and quickly communicated between communications devices by obviating the need for user data to be relayed by a network entity such as a base station. D2D communications also allow communications devices to communicate with one another even when one or both devices may not be within the reliable coverage area of a network. The ability for communications devices to operate both inside and outside of coverage areas makes wireless telecommunications systems that incorporate D2D capabilities well suited to applications such as public protection/safety and disaster relief (PPDR), for example. PPDR related communications may benefit from a high degree of robustness whereby devices can continue to communicate with one another in congested networks and when outside a coverage area. 3GPP has developed some proposals for such public safety D2D use in LTE networks in Release12.
The automotive industry has been working for several years on solutions to enable communication with and between vehicles, e.g. to help improve traffic flow and safety. These techniques can range from automatic tolling technologies to collision prevention mechanisms, and are generally known as Intelligent Transport Systems (ITS). Currently, the main radio technology under consideration in standards projects relating to ITS is a WLAN derivative 802.11p, which would be used for broadcasting ITS information by vehicles or road side infrastructure to other vehicles. This constitutes so-called Dedicated Short Range Communication (DSRC) system that is deployed at 5.9 GHz ITS band in Europe and North America (there may be different ITS bands in use in other regions, e.g. 700 MHz in Japan).
The effective range of DSRC systems is a few hundred meters and the services are broadcast oriented (emergency vehicle notices, for example).
However, there have also been proposals for communications based on those used in mobile telecommunications systems, such as Long Term Evolution (LTE) based networks operating on International Mobile Telecommunications (IMT) bands, to help support ITS applications, for example to provide more capacity and potentially provide for wider and cheaper coverage. In particular, where the existing cellular network already covers roadways the capital expenditure costs associated with using cellular mobile telecommunications techniques for ITS applications may be significantly less than what would be needed for setting up a new DSRC-based ITS network.
Accordingly, an Intelligent Transport System may rely on D2D communications of the kind proposed for mobile wireless telecommunications systems to allow vehicles to communicate with one another and with other terminal devices or network infrastructure equipment, such as a base station or specific road side infrastructure. In this regard, communications associated with connected vehicle systems may be conveniently referred to as V2X (vehicle-to-everything) communications, which may comprise V2V (vehicle-to-vehicle), V2P (vehicle-to-pedestrian) and V2I (vehicle-to-infrastructure). Infrastructure in this case may be a roadside ITS related infrastructure element, which may be referred to as a road side unit (RSU), or a conventional Internet or mobile network infrastructure element. Some examples or services in connected a vehicle context are Cooperative Awareness Message (CAM) and Decentralised Environmental Notification (DEN). These constitute applications such as allowing emergency vehicles to broadcast their presence and allowing roadside infrastructure to broadcast speed limit information to vehicles.
It has been proposed that V2X communications may be implemented using dedicated Road Side Units (RSUs) which communicate with vehicles and which assign radio resources for use by the vehicles in V2X communications. In particular, such RSUs may allocate D2D radio resources for use in V2X communications. Nonetheless, it is also to be expected that there may be situations where vehicles will wish to autonomously communicate directly with one another (V2V) without any network infrastructure interaction, for example because not all the roadways may have RSUs installed, particularly in more rural areas. V2X or V2X-like communications between vehicle can however have the combined specificity that the communicating terminals may each be at a fairly low elevation (for example about 1.5 m) and that the communications may be related to safety and therefore critical and/or high priority. Due to the low height or elevation, it can be difficult to achieve line of sight (“LOS”) conditions between the terminals because of obstacles around the terminals and, as a result, the terminals may not be able to communicate with each other or maybe not until a later point in time. This aspect combined with the potentially high priority or the critical level of the V2X communications can result in high safety risk. Arrangements which are able to consider obstacles can thus assist with a suitable flow of traffic between terminals and with promoting safety in a V2X environment.